Towards a new generation of mid-infrared photonics systems

Published: 28 May 2014

New published results from the EU funded project, CLARITY, will help photonics researchers better understand and improve quantum cascade lasers (QCLs) and mid-infrared fibers, and provide the basis for highly efficient mid- to near-infrared conversion.

Following the invention of the quantum cascade laser (QCL) in 1994, the mid-infrared (mid-IR) spectral region has attracted a significant amount of interest for tunable diode laser spectroscopy and optical communication. Compared to their near-infrared counterparts however, mid-infrared technologies are still relatively immature and the mid-IR region has continued to suffer from a lack of suitably fast detectors for spectroscopy and optical communication.

Within the framework of a European Union-funded research project called CLARITY (Compact uLtrA-efficient mid-infRared photonIc sysTems based on low noise quantum cascade laser sources, wide band frequencY converters and near infrared photodetectors); these deficiencies have been addressed and their latest results are helping researchers to better understand and improve quantum cascade lasers and mid-infrared fibers. The groundwork for highly efficient mid- to near-infrared conversion has been laid.

Highlights of the achievements are a reduction of the relative intensity noise of a quantum cascade laser by 9.5 dB demonstrated in an injection locking experiment, development of first continuous wave emitting distributed-feedback QCL arrays with a tunablity of typically more than 100 cm-1 enabling multi-gas and heavy molecule spectroscopy, demonstration of a significant loss-reduction of telluride glass fibers in the 3-4 µm range, and conversion from 2650 nm to 1770 nm in SiGe-based nanowaveguides.

The latter is especially of interest in addressing the lack of suitably fast detectors for spectroscopy and optical communication within the mid-IR range. The specifications (noise level, response time etc) of the widespread mercury cadmium telluride detectors are orders of magnitude worse than their pendants in the near-infrared. Therefore a conversion of mid- to infrared light is desired to be able to utilize the advantages of highly sophisticated near-infrared detector technology. The conducted experiments and good agreement with theoretical predictions let the consortium believe that in the near future wavelengths conversions with record performance will be demonstrated so that silicon based nonlinear converters will soon outperform traditional mid-infrared detectors.

The CLARITY project started in September 2011 and the consortium consists of six research organizations from Greece (National and Kapodistrian University of Athens), France (III-V Lab and CEA-LETI), Germany (Technische Universität Darmstadt), UK (Optoelectronics Research Centre, University of Southampton), and Norway (Norsk Elektro Optikk).